--- kernel/compat.c

+++ kernel/compat.c

@@ -25,6 +25,7 @@

#include <linux/posix-timers.h>

#include <linux/times.h>

#include <linux/ptrace.h>

+#include <linux/module.h>

#include <asm/uaccess.h>

@@ -1136,3 +1137,24 @@ compat_sys_sysinfo(struct compat_sysinfo

return 0;

}

+

+/*

+ * Allocate user-space memory for the duration of a single system call,

+ * in order to marshall parameters inside a compat thunk.

+ */

+void __user *compat_alloc_user_space(unsigned long len)

+{

+ void __user *ptr;

+

+ /* If len would occupy more than half of the entire compat space... */

+ if (unlikely(len > (((compat_uptr_t)~0) >> 1)))

+ return NULL;

+

+ ptr = arch_compat_alloc_user_space(len);

+

+ if (unlikely(!access_ok(VERIFY_WRITE, ptr, len)))

+ return NULL;

+

+ return ptr;

+}

+EXPORT_SYMBOL_GPL(compat_alloc_user_space);